A panel for use in a square type cathode ray tube, for example, a cylindrical panel 1 of FIG. 1 and a spherical panel 2 of FIG. 2 are each formed of face portions 4 which are respectively formed as cylindrical and spherical curved surfaces and skirt portions 5. As shown in FIG. 3, such panel is a molded product that is provided by filling a melted glass 9 into a metal mold formed of a bottom 7 and a shell ring 8 and then pressing the melted glass 9 by a plunger 10. In accordance with the shape of the connected portion between the bottom 7 and the shell ring 8, the molded panel is given with a mold match line 3 which is a ridge line taking the form of gentle convexity. As shown in FIGS. 1 and 2, the mold match line 3 of the prior art panel is a straight line which runs in parallel to an end surface 11 thereof connected with a funnel portion. After this panel is assembled with the funnel portion to thereby construct the cathode ray tube, a tension band 16 is wound around the mold match line 3, whereby to reinforce the implosion protection of the cathode ray tube. The tension by the tension band 16 causes a compression force within the surface of the face portion 4 and produces a stress against the external force. However, when the tension band 16 is wound around the prior art panel, a tension F thereof is concentrated on the mold match line 3 of straight line shape. As a result, as shown in FIG. 5, at the corner portion where the mold match line 3 and the face portion 4 are close to each other, the tension F is transmitted to the face portion 4, while at central regions 12, 14 and 13 of the side portions of the face portion 4 remote from the mold match line 3 with large distances of ha, hb and hc, the tension F is not effectively transmitted to the face portion as shown in FIG. 4 so that the stresses caused by high atmospheric pressure and impact force can not be reduced so much. Particularly, when as shown in FIGS. 1 and 2, the tension band 16 has a uniform width over the entire periphery of the panel and the both upper and lower sides thereof are made in parallel to each other, the above-described problem exists in a standpoint for reinforcing implosion protection of the cathode ray tube.
In view of the above-described aspect, this invention is to provide a cathode ray tube in which the tension by a tension band over a mold match line can effectively be transmitted to the entire periphery of a face portion of a panel so that a resistance of the face portion against an external force can be increased to thereby increase the implosion protection.